1. Field of the Invention
The present invention relates generally to semiconductor wafer cleaning and, more particularly, a chuck assembly to be utilized in semiconductor substrate spin, rinse, and dry (SRD) modules.
2. Description of the Related Art
Wafer preparation and cleaning operations are performed in the fabrication of semiconductor devices. One commonly used wafer preparation operation used at various stages of substrate preparation is a spin, rinse, and dry (SRD) module. Conventionally, the wafer is spin rinsed by spraying deionized water onto the top and backside of the wafer, as the wafer is spun around at high speed. The spin rinse operations are typically performed in a bowl rigidly mounted on an SRD housing designed to receive a spindle coupled to a motor. As the motor rotates, so do the spindle, a chuck mounted on the spindle, and the wafer. Customarily, the chuck supports the edges of the wafer by utilizing four spindle fingers coupled to the chuck. The spindle fingers are designed to move upwardly out of the bowl such that they extend outside the bowl housing. Thus, customarily, the wafer is delivered to the spindle fingers while they are extended out side of the bowl at a level above wafer processing plane. Once the wafer is delivered to the spindle fingers, the chuck having the spindle fingers and wafer attached thereto moves back down and into the bowl so as to place the wafer at the level of wafer processing plane.
Typically, fluid (e.g., DI water) is supplied to a spigot and thus onto the surface of the wafer, as the wafer is spun at high revolutions per minute (RPMs). When the surface of the wafer is sprayed with fluid, the supplying of fluid is stopped by turning off the spigot, and the wafer is dried as the wafer continues to spin at high RPMs. Once the wafer is dried, the processed wafer is unloaded by moving the chuck and spindle fingers holding the wafer upwardly out of the bowl until the wafer is extended above the wafer process plane for a second time. At this time, an end effector can reach in and remove the wafer from the SRD module.
Numerous shortcomings can be associated with chuck assemblies of conventional SRD modules. Primarily, the typical SRD module requires a complex chuck design. For instance, the chuck is commonly required to move up and down. The chuck moves up to receive the wafer, moves down to process the wafer and then up again to remove the wafer from the SRD bowl. In view of this continual movement activity, it is imperative that the chuck remain properly calibrated so that it comes to rest at the exact process level. In situations where the chuck is not properly aligned, failure to properly receive and deliver the wafer mandates the realignment of the chuck. The process of realigning of the chuck is very time consuming and labor intensive, and it requires that the SRD module be taken off-line for an extended period of time, thus reducing throughput.
Another shortcoming of conventional chucks is the unnecessary movements required in loading and unloading of the wafer to and from the fixed spindle fingers. Predominantly, in conventional SRD modules, the loading of the wafer onto the fixed spindle fingers involves four stages. That is, to receive a wafer, initially, the chuck is moved upwardly and out of the bowl, such that the chuck is positioned above the wafer process plane. As a result of having fixed spindle fingers to deliver the unprocessed wafer to the edges of the spindle fingers, at the outset, the end effector having the wafer is moved horizontally over the bowl at a level that is above the horizontal plane of the spindle fingers (which are already in the up position). Thereafter, the end effector must move downwardly (while over the bowl) until the wafer reaches the level of the spindle finger. At this point, the spindle fingers can engage the wafer. Once the spindle fingers have engaged the wafer, the end effector relinquishes the wafer and thus physically delivering the unprocessed wafer to the spindle fingers. Finally, to pull out, the end effector is required to move slightly down and away from the wafer under surface before moving horizontally away from over the bowl. Each of the up and down movements of the end effector are performed using the xe2x80x9cZxe2x80x9d speed of the end effector, which in fact is a significantly low speed. As such, the performing of a spin, rinse and dry operation on each wafer requires a significant amount of time simply to load and unload the wafer, thus increasing the SRD cycle per wafer. As can be appreciated, this reduces the overall throughput of the SRD module.
Yet another shortcoming associated with conventional chucks of SRD modules is the creation of air turbulence above the wafer surface. That is, as the chuck and thus the wafer spin in the bowl, the spinning action of the chuck and the wafer transfer energy to air flowing over the top side of the wafer. This transferred energy causes the airflow above the topside of the wafer to become turbulent and thus creates recirculating air (i.e., eddies). The amount of energy transferred to the air flowing to the topside of the wafer depends on the diameter and the rotational speed of the wafer. In general, the greater the amount of energy transferred to the air, the higher the eddies extend above the topside and the farther the eddies extend below the backside of the wafer. The presence of eddies below the wafer is undesirable because particles or DI water droplets removed from the wafer can circulate in the eddies and can be re-deposited on the backside of the wafer, thereby causing wafer recontamination.
Further challenges faced in the use of conventional flat chucks are the limitations associated with the chuck geometry. Mainly, the relatively large size and associated weight of conventional flat chucks necessitate the use of significantly higher amounts of energy to operate the SRD module. Additionally, the large size of the chuck further requires the use of larger shafts as well as spindles. Collectively, these limitations mandate the use of a larger and more powerful motor, thus increasing the cost of the SRD modules as well as the associated operating cost.
Yet another challenge faced in the use of flat chucks in SRD modules is having chemically incompatible components present within the modules. In a typical SRD module, most components are constructed from several different materials. For instance, the chuck is usually constructed from Aluminum, while the bowl is made out of Polyurethane, and the spigot is made out of stainless steal. As a result, particles or contaminants from chemically incompatible components may enter into chemical reaction with the fluids introduced into the SRD module, thus further recontaminating the SRD module. This recontamination can further be exacerbated by the aluminum chuck having to continuously move up and down (e.g., to load and unload each new wafer) within the bowl. That is, as the chuck moves up and down within the bowl, some of its coating may flake off of the chuck, thus generating particulates and contaminants inside the bowl and the SRD module. In some cases, these contaminants may react with the residual chemicals (e.g., HF, NH3OH, etc.) present in the SRD module from previous brush scrubbing operations. It is believed that these chemical reactions between the residual chemicals and the generated particulates and contaminants of the chuck may cause the recontamination of the wafer as well as the SRD module.
In view of the foregoing, a need therefore exists in the art for a chemically compatible chuck assembly that improves the spin, rinse, and dry operations performed on the surfaces of substrates while reducing the risk of wafer contamination.
Broadly speaking, the present invention fills these needs by providing an apparatus and related methods for optimizing the spin, rinse, and dry operations of a spin, rinse, and dry (SRD) module. The SRD module implements a chuck assembly constructed from chemically compatible material designed to facilitate and expedite the operations of the SRD module. Preferably, the chuck assembly is configured to operate with less mechanical movements during load and unload stages, thus accelerating the overall time of spin, rinse, and dry operations of the SRD module. In one implementation, the chuck assembly includes a plurality of grippers configured to hold the wafer to be processed. Preferably, in one embodiment, the grippers are designed to rotate about a fixed pin and are configured to assume a substantially flat position at the instances wherein a substrate is being delivered or picked up. When the substrate is to be processed, the grippers are designed to move to an upright position so as to engage the substrate.
In yet another embodiment, the geometry of the chuck assembly is configured to be cylindrical so as to reduce air turbulence above the wafer surface. In still a different implementation, the inertia of the chuck assembly is reduced, thus substantially significantly lowering the amount of energy required to operate the chuck. Preferably, in one embodiment, the inertia is reduced through decreasing the weight of the chuck assembly by hogging out portions of the inner portion of the chuck body, thus enabling the implementation of a substantially smaller motor to operate the chuck assembly.
It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, A chuck assembly for use in preparing a substrate is disclosed. The chuck assembly includes a chuck body, a chuck top plate, a plurality of grippers, and a conical-type wedge. The chuck body is designed to have a cylindrical shape configured to reduce air disturbance around a surface of the substrate. The chuck body also has an outer ring and an inner ring. The outer ring is connected to the inner ring with a plurality of spokes, each of which is configured to house a linkage arm. The chuck top plate has a ring and is configured to be attached to a top surface of the chuck body. Each gripper is coupled to the chuck body with a rotation pin and to the respective linkage arm with a linkage pin. Each gripper is configured to pivot about the respective rotation pin between a substantially upright position and a substantially flat position so as to engage or disengage the substrate. The conical-type wedge has an angled sidewall and a substantially central throughbore. A radius at a top region of the conical-type wedge is greater than a radius at a bottom region of the conical-type wedge. The conical-type wedge is configured to move between a lower position and an upper position. In the lower position, the grippers are at the substantially upright position and in the upper position, the grippers are at the substantially flat position.
In another embodiment, a chuck assembly for use in a substrate spin, rinse, and dry (SRD) module is disclosed. The chuck assembly includes a wedge, a chuck body, and a plurality of grippers. The wedge has a sidewall and is configured to move from a lower position to an upper position and from the upper position to the lower position thus opening and closing the chuck assembly, respectively. The chuck body has a cylindrical shape and is configured to include a plurality of linkage arms. The chuck body is configured to enclose the wedge such that each linkage arm is substantially in contact with the sidewall of the wedge. The cylindrical shape of the chuck body is configured to reduce air disturbance around a surface of a substrate. The plurality of grippers are configured to be coupled to the chuck body via a plurality of rotation pins. Each of the grippers is configured to stand substantially upright so as to engage the substrate when the wedge is in a lower position. Each of the grippers is configured to lie substantially flat so as to disengage the substrate when the wedge is in the lower position.
In yet another embodiment, a chuck assembly for use in preparing a substrate is disclosed. The chuck assembly includes a chuck body, a chuck top plate, a wafer backside plate, a plurality of grippers, and a wedge. The chuck body is designed to have a cylindrical shape configured to reduce air disturbance around a surface of the substrate. The chuck body has an outer ring and an inner ring. The outer ring is connected to the inner ring with a plurality of spokes, each of which is configured to house a linkage arm. The chuck top plate has a ring and is configured to be attached to a top surface of the chuck body. The wafer backside plate has a cylindrical-disk shape and is configured to be defined on a top surface of the chuck top plate. Each gripper is coupled to the chuck body with a rotation pin and to the respective linkage arm with a linkage pin. Each gripper is configured to pivot about the respective rotation pin between a substantially upright position and a substantially flat position so as to engage or disengage the substrate. The wedge has an angled sidewall and a substantially central throughbore. A radius at a top region of the wedge is greater than a radius at a bottom region of the wedge. The wedge is configured to move between a lower position and an upper position. In the lower position, the grippers are at the substantially upright position and in the upper position, the grippers are at the substantially flat position.
In still a further embodiment, an apparatus is disclosed. The apparatus includes a wedge, a chuck body, a wafer backside plate, and a plurality of grippers. The wedge has a sidewall and is configured to open and close the chuck assembly by moving from a lower position to an upper position and from the upper position to the lower position, respectively. The chuck body has a cylindrical shape and is configured to include a plurality of linkage arms. The chuck body is configured to enclose the wedge such that each linkage arm is configured to be substantially in contact with the sidewall of the wedge. The cylindrical shape of the chuck body is configured to reduce air disturbance around a surface of a substrate. The wafer backside plate is configured to include a cylindrical edge lip that defines a central aperture. The plurality of grippers are configured to be coupled to the chuck body via a plurality of rotation pins. Each of the grippers is configured to stand substantially upright so as to engage the substrate when the wedge is in the lower position. Each of the grippers is configured to lie substantially flat so as to disengage a substrate when the wedge is in the lower position.
In still a further embodiment, a method for making a chuck body for spinning a wafer is disclosed. In this method, a cylindrical disk is provided. The cylindrical disk is then machined to form an outer ring, an inner ring and a plurality of spokes. A linkage arm having an outer end and an inner end is then integrated in each of the plurality of spokes. A gripper is then attached to each outer end of each linkage arm. Each gripper is configured to rotate about a rotation pin that is connected to an edge of the outer ring. The outer end of the linkage arm is connected to the gripper by a linkage pin. Each gripper is configured to rotate between a substantially flat position when in a load or unload position and a substantially upright position when engaging the wafer.
In still another embodiment, a method for making a chuck for spinning a wafer is disclosed. In this method, a disk is machined. The machining is configured to hog-out a center portion of the disk to define an inner ring and inner ribs to define a plurality of spokes and an outer ring. Channels are then machined in each of the spokes and a linkage arm is then inserted in each channel of each spoke. Then, a gripper is attached to an outer end of each linkage arm. The grippers are defined along the outer ring and are configured to move between a substantially flat position and a substantially upright position.
In still another embodiment, a method for making a chuck for spinning a wafer is disclosed. In this method, a disk is machined. The machining is configured to hog-out a center portion of the disk to define an inner ring and inner ribs to define a plurality of spokes and an outer ring. Channels are then machined in each of the spokes and a linkage arm is then inserted in each channel of each spoke. Then, a gripper is attached to an outer end of each linkage arm. The grippers are defined along the outer ring and are configured to move between a substantially flat position and a substantially upright position. Thereafter, a plate having a shape substantially similar to the disk is attached to a top surface of the disk.
In yet another embodiment, a method for making a chuck for spinning a wafer is disclosed. In this method, a disk is machined. The machining is configured to hog-out a center portion of the disk to define an inner ring and inner ribs to define a plurality of spokes and an outer ring. Channels are then machined in each of the spokes and a linkage arm is then inserted in each channel of each spoke. Then, a gripper is attached to an outer end of each linkage arm. The grippers are defined along the outer ring and are configured to move between a substantially flat position and a substantially upright position. Thereafter, a plate having a shape substantially similar to the disk is attached to a top surface of the disk. Then, a second plate having a shape substantially similar to the disk is defined on a top surface of the first plate.
The advantages of the present invention are numerous. Most notably, unlike conventional chucks, the chuck assembly of the present invention implements less mechanical movements in loading and unloading of substrates, thus increasing the throughput of the SRD module. Particularly, instead of using fixed spindle fingers, the chuck assembly of the present invention implements a plurality of grippers capable of rotating about a rotating pin such that the grippers can assume: (a) a substantially flat position during the loading and unloading of substrates, thus eliminating the need for moving the grippers and chuck up and down; and (b) a substantially upright position so as to engage a substrate to processed. Thus, the embodiments of the present invention reduce the length of each spin, rinse, and dry cycle, thereby increasing the throughput of the SRD module. Another advantage of the chuck assembly of the present invention is that unlike conventional SRD modules in which the chuck assembly moves vertically to deliver or receive a wafer to be processed, the chuck assembly remains fixed. To move the grippers between a load/unload position and a process position, the present invention implements a wedge located at about the center of the chuck. Yet another advantage of the chuck assembly of the present invention is that the components of the chuck assembly are constructed from chemically compatible materials. Still another benefit of the chuck assembly of the present invention is that unlike conventional SRD modules which implement flat chucks, the chuck assembly of the present invention implements a cylindrical chuck including hogged out ribs, thus reducing the inertia of the chuck assembly, thereby enabling the use of a less powerful motor to operate the chuck assembly. Ultimately, the geometry of the chuck assembly of the present invention is configured to reduce air turbulence above the substrate surface, thus reducing wafer surface recontamination.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.